1. Field of the Invention
The present invention relates to methods and means for the in situ repair of mechanical seals of the type currently used in effecting an interface between two pieces of equipment between which there is relative movement, including a moving shaft and the housing through which it passes. Such a seal assembly, in one embodiment thereof, comprises a two-component arrangement with one portion thereof attached by any convenient means to a pump casing and the other portion thereof attached by any of a number of convenient means to the rotating pump shaft, said rotating pump shaft normally being in operative association with drive means therefore. One commercially available configuration of such a seal assembly may take the general form of two rings with the inside diameters and the outside diameters of each ring being approximately equal, one to the other, each of said rings having at least one flat side thereof, the width of said at least one flat side thereof being generally defined by said inside and outside diameters, said rings being concentric about a common axis and spaced longitudinally there along in juxtaposition with one another to effect a mating relationship between the at least one flat side, i.e., seal face, of each such ring. In many such type of assemblies, the use of resilient means, such as springs, are employed in a manner so as to urge or nudge said rings together. In operation, the surfaces of said rings, in juxtaposition with one another move relative to one another, i.e., one of said rings will rotate in unison with the pump shaft and the other is in stationary relationship along with the pump casing. After prolonged usage of such seal assemblies, the original closely mating surfaces thereof which provide the sealing means, i.e., the seal faces, are disrupted by the debris ingesting conditions normally presented by the fluid sealed thereby. Such disruptions may take the form of debris, such as suspended particulate matter, along with grease and/or grime carried in such fluid or on the surfaces such particulate matter, rust, or scale subsequently formed within the pumping loop, being physically lodged between said mating surfaces thereby effecting the wedging of same apart one from the other. Such disruptions may also take the form of minute, but significant indentations in the otherwise essentially optically flat seal face surfaces, which apparently result from the scratching or scoring action provided by the movement of particles of such debris over such surfaces. The net result of such wedging of such particles between the seal faces and/or the resulting scoring thereof results in subsequent leakage of fluid through the seal. The practice of the present invention repairs or corrects the deleterious effects of such disruptions by the use of the instant new mechanical SLP which is produced by the compounding of a relatively few, inexpensive, and readily available materials and requires only a minimal amount of relatively inexpensive equipment for the proper application thereof. The instant invention is simply and easily placed into practice by, for example, applying relatively small amounts of such compound to the outside or peripheral portions of the sealing surfaces, i.e., at the outermost juncture of the interface between said rings wherein they are juxtaposed with one another and move relative to one another. It has been found that a hypodermic needle can be used to send a fine stream of said SLP to said interface, or a misting device, such as an aerosol sprayer can be used to apply said SLP. It has also been discovered quite unexpectedly, that the instant, new, and novel SLP works completely satisfactorily and successfully even though it is applied to the juncture of said seal faces only at the outermost portion thereof, i.e., at the periphery, and even while such pumps are in active operation. The fact that the instant invention works at all seems to defy certain of the basic laws of physics when it is realized that oftentimes the moving seal face, of the two faces comprising such type of mechanical seals, is normally rotating at substantial speed and the resulting centrifugal forces that would be imparted to any material applied thereon would tend to sling same outward and away from the contact surfaces of the seal, rather than allowing such material, including the fluid comprising said SLP, to penetrate same. It should also be appreciated that the fluid which is contained by the seal is generally under considerable pressure and when a seal begins to leak such pressure will, of course, cause the fluid to exit the assembly at a rather rapid rate and thereby tend to carry away material applied to the outside thereof. I am not cognizant of a theory to readily explain this unexpected result and observation in and of the practice of my invention-perhaps the application of the SLP to the outside of the seal assembly so alters the contact angle, or other surface tension characteristics of the fluid leaking therefrom so as to allow for the penetration of the SLP either alone or in combination with some portion of fluid leaking therefrom, into and onto the juxtaposed seal faces to thereby effect the principal objectives of the instant invention. In any event, the application of said SLP to such seal assemblies has been observed, in extensive testing thereof, to either completely eliminate or to at least substantially reduce such leaking to a point wherein it is so minute or inconsequential so as not to present any danger to attendant equipment nor to be of a significant health or safety concern. It is believed that several mechanisms are at work as said SLP effects the desired and required results. In the first place, the SLP is able to penetrate the seal assembly, while same is in operating mode, so as to be placed in the proper location to repair or correct the unwanted and undesired leaking thereof. In the second place, the SLP effectively acts upon any debris caught or wedged between the faces of such assembly to cause same to be flushed away. In the third place, the SLP acts upon the surfaces of the seal faces in a manner analogous to a lapping compound to resurface or smooth such damaged faces.
2. Description of the Prior Art
The operation of a multitude of fluid chemical process and handling equipment wherein are located rotating parts and, in particular, wherein are located mechanical interfaces between such rotating parts and parts that are either stationary or which move relative to such rotating parts, has required the design and utilization of a variety of sealing means therefore. Many of such prior art arrangements are disclosed in the literature and involved numerous designs and variations of earlier designs which utilized packing arrangements. Although such arrangements did effect sealing, they were fraught with the inherent difficulty of not providing zero leakage around pump shafts, and the like, which oftentimes resulted in the causing of excessive wear of the pump shaft or sleeve.
Many years ago, as the evolution of seal designs progressed, the mechanical seal of the type herein described and referenced came into common usage. Although there are numerous arrangements and designs for such modern day mechanical seals, for the purposes of the following discussions and descriptions of the instant invention and how same is practiced, and in the interest of brevity and conciseness, these descriptions will be directed to a seal design of the general configuration, infra, it being understood that the instant invention is not necessarily limited thereto. Such seal design and assembly generally comprises the form of two rings, with the inside diameters of each ring being about equal, and the outside diameters of each ring being about equal. Each of said rings has at least a first flat side thereof, with the width of said at least first flat side being generally defined by said inside and outside ring diameters, i.e., the width of each ring approximates the length difference represented by said inside and outside diameters. The rings are arranged concentrically about a common axis, which is usually the same axis as the pump shaft, and are spaced together so as to effect a mating relationship between the at least one flat side of each such ring. Said at least first flat side of each ring, generally known as the seal face, is provided with an extremely flat surface, even approaching optically flat, so as to present to the equally flat surface of the oppositely facing ring a surface capable of joining therewith for forming a sliding sealing surface interface. To ensure that the two surfaces slide past one another with consummate ease, i.e., the coefficient of sliding friction is as low as possible, the seal face materials of construction, or at least of facing, may be different from one another. For instance, the stationary face material may be silicon carbide, tungsten carbide, or ceramic; whereas, the rotary face material may be carbon, silicon carbide, or ceramic. The side of each ring disposed opposite to each respective at least first flat side, as well as in some designs at least a portion of the peripheral surface thereof, is generally arranged in sealed relationship with the respective housing attendant each ring. In many such type of assemblies, the use of resilient means such as springs are employed in a manner so as to urge or nudge the seal faces of said rings together.
In operation, the surfaces of said rings, in juxtaposition with one another, i.e., the seal faces, move relative to one another. For instance, one of said rings will rotate in unison with the pump shaft and the other is in stationary relationship with the pump casing. It will be appreciated that this design of seal assemblies is far superior to that of earlier designs which utilized a variety of packing arrangements. It will also be appreciated by those skilled in this art that, superior as this later design may be over earlier arrangements, after prolonged usage of such seal assemblies the original closely mating surfaces thereof, which provide the sealing means, are disrupted by the debris ingesting conditions normally presented by the fluid sealed thereby. Such disruptions may take the form of debris such as suspended particulate matter carried in such fluid, or rust or scale subsequently formed within the pumping loop, being physically lodged between said mating surfaces, thereby effecting the wedging of same apart, one from the other. Such disruptions may also take the form of minute, but significant, indentations in the otherwise essentially optically flat seal face surfaces which apparently result from the scratching or scoring action provided by the movement of particles of such debris over such surfaces.
As may well be appreciated by those skilled in this art, undoubtedly there have been numerous prior art investigators who have sought to discover any method and/or means for attempting the repairing of leaking mechanical seals of the type just described, supra, with particular emphasis on the effecting of such leaks while such seal assemblies are in operation and the equipment to which they are operatively associated is online. In searching the literature, both formal and that comprising vendors catalogs, I have been unable to find any reference to mechanisms, methods, or means for effecting such repairs, short of taking the pump unit offline and disassembling same to remove the leaking mechanical seal and replacing same with a new one. Likewise, a search of such references has not revealed the existence of, nor even an inference to any compound, mixture, or other product represented by any reputable manufacturer which will prolong the life of such a leaking seal by stopping same from leaking for an extended period of time so as to allow same to remain online until a more opportune time to effect such disassembly presents itself. In the instance of such a seal leaking in any number of critical areas of an electric generating unit, such as a fossil-fueled or nuclear-powered steam plant, such a more opportune time would be when the load on the system in which such unit is networked is not critical or when there exists a preplanned outage for effecting regularly scheduled maintenance and repair.
In German Offen. DE 3,447,346 A1, Fahl, June 26, 1986, there is taught new high-viscosity lubricants for use on water line fittings such as valves, pumps, etc., which appear to yield service lives perhaps some four times that of other lubricants tested. These teachings disclose that such new lubricants comprise basically the following four categories (1) a thickener (optional)--can include metal soaps, polyurea, polytetrafluorethylene, montmorillonite and mixtures thereof (20 weight percent); (2) a lubricant (base component)--can include a naturally occurring (paraffinic white oil), or synthetic high-viscosity lubricating (polymeric) oil; (3) a complexing agent to remove the Ca.sup.+2 and/or the Fe.sub.2 O.sub.3 --can include polyphosphoric acid, amino acid, derivatives of acetic acid polyamine (i.e., ethyelenediamenetetraacetic acid, nitrilotriacteic acid, etc.), and mixtures thereof (0.3-3, preferably 0.5-1.5 weight percent); and (4) a water proofing agent--can include tall oil resins, an alkyd resin, and mixtures thereof. This water-proofing material may be a necessary component when (2), supra, is not a silicone base material (0-12, preferably 2-10 weight percent). As will be seen, infra, and appreciated after thoroughly reading the full disclosure herein, the compound of the instant invention, including the instant new SLP, although utilizing a soap and a dilute source of acetic acid, cannot be of high-viscosity. Therefore, the use of either a high-viscosity silicone oil or grease, as taught in Fahl, supra, is contrary to the instant teachings. Furthermore, his high-viscosity silicone material comprises some 80 percent of his lubricant, whereas the relatively low-viscosity silicone oil utilized in the preparation of the instant SLP, most preferably comprises only about 20 percent thereof. Also, Fahl uses his soap as a thickener and in amounts of about 20 percent, on a weight basis, as opposed to the instant invention which uses about 40 percent on a volume basis. Likewise, he uses less than about 3 percent--preferably 1.5 percent of a complexing agent as opposed to the instant invention which uses some 10 percent thereof. In addition, it will be appreciated that Fahl teaches the use of, as his water proofing agent, quite different materials, i.e., tall oil or alkyd resins as opposed to the instant invention which uses lemon and/or orange peel oil. It will be further appreciated that Fahl does not teach the use of a penetrant, such as the instant inventions use of Kroil.RTM.. Finally, it will be appreciated that although the lubricant taught by Fahl obviously will prolong the life of certain water line fittings, there is no teaching, or even inference, that same can be utilized in the system or in the manner taught in the instant invention.